题目解析：
【题目翻译】根据第3段，反对“保护主义”假设的人的立场是什么？
A：花外花蜜为植物提供了直接防御昆虫攻击的能力。
B：蚂蚁对分泌花外花蜜的植物大有好处。
C：花外花蜜的分泌对植物的内部功能起着一定的作用。
D：蚂蚁访问分泌花外花蜜的植物和访问不分泌花外花蜜的植物一样频繁。
【判定题型】：题目问的是文章中的具体细节信息，故根据题目问法可以判断本题为事实信息题。
【关键词定位】：根据关键词“the opponents of the “protectionist” hypothesis”,定位到Passage3第2句，原句为“This view and the opposing “protectionist” hypothesis that ants defend plants had been disputed for over a hundred years when, in 1910, a skeptical William Morton Wheeler commented on the controversy. ”，意思是“人们就该观点及其反方观点争执了很多年。反方观点坚持“保护主义者”假说，认为蚂蚁能够保护植物。1910年，怀疑论者威廉莫尔顿惠勒对这一争议做出了评论。”
【逻辑分析】但是定位句这句话只说了这个观点和保护主义假说的反对意见受到争议，所以他们具体的立场应该看首句Biologists once thought that secretion of extrafloral nectar has some purely internal physiological function, and that ants provide no benefit whatsoever to the plants that secrete it.
【选项分析】
A.是内部功能不是外部防御昆虫，故错误。
B.不是花外，是花的内部功能，故错误。
C.文章说：外部花蜜的分泌物只是对植物有内部生理作用，蚂蚁没有作用，对应C选项。
D.文章未提及两者的频率，也未比较，故错误。
Biologists once thought that secretion of extrafloral nectar has some purely internal physiological function, and that ants provide no benefit whatsoever to the plants that secrete it. This view and the opposing “protectionist” hypothesis that ants defend plants had been disputed for over a hundred years when, in 1910, a skeptical William Morton Wheeler commented on the controversy. He called for proof of the protectionist view: that visitations of the ants confer protection on the plants and that in the absence of the insects a much greater number would perish or fail to produce flowers or seeds than when the insects are present. That we now have an abundance of the proof that was called for was established when Barbara Bentley reviewed the relevant evidence in 1977, and since then many more observations and experiments have provided still further proof that ants benefit plants.
